Enterobactin is a siderophore produced by enteric bacteria to trap ferric ions under iron-deficient conditions and has the following structure: ##STR2##
Enterobactin exhibits unique chemical properties including (1) the extraordinarily high affinity for ferric ions (stability constant (K.sub.f) of ferric enterobactin being -10.sup.49) and (2) the chirality at the metal center with the exclusively right-handed (A) configuration. The unnatural antipode of enterobactin was shown to lack biological activities, suggesting that the chirality at the metal center plays an important role.
There have been substantial efforts in synthesizing enterobactin analogs. In particular, enterobactin analogs with enhanced lipophilicity may affect the tissue distribution of the metal complex and will have various medical applications.